1. Technical Field
The present disclosure relates to surgical instruments and, more particularly, to lever latch mechanisms for use with a surgical forceps for sealing and/or dividing various tissue structures.
2. Description of Related Art
Surgical forceps utilize both mechanical clamping action and electrical energy to affect hemostasis by heating the tissue and blood vessels to coagulate, cauterize and/or seal tissue. Many surgical procedures require cutting and/or ligating large blood vessels and large tissue structures. Due to the inherent spatial considerations of the surgical cavity, surgeons often have difficulty suturing vessels or performing other traditional methods of controlling bleeding, e.g., clamping and/or tying-off transected blood vessels or tissue. By utilizing an electrosurgical forceps, a surgeon can either cauterize, coagulate/desiccate and/or simply reduce or slow bleeding by controlling the intensity, frequency and duration of the electrosurgical energy applied through the jaw members to the tissue. Most small blood vessels, i.e., in the range below two millimeters in diameter, can often be closed using standard electrosurgical instruments and techniques. However, larger vessels can be more difficult to close using these standard techniques.
In order to resolve many of the known issues described above and other issues relevant to cauterization and coagulation, a recently developed technology has been developed called vessel or tissue sealing. The process of coagulating vessels is fundamentally different than electrosurgical vessel sealing. For the purposes herein, “coagulation” is defined as a process of desiccating tissue wherein the tissue cells are ruptured and dried. “Vessel sealing” or “tissue sealing” is defined as the process of liquefying the collagen in the tissue so that it reforms into a fused mass with limited demarcation between opposing tissue structures. Coagulation of small vessels is sufficient to permanently close them, while larger vessels and tissue need to be sealed to assure permanent closure.
In order to effectively seal larger vessels (or tissue) two predominant mechanical parameters are accurately controlled: 1) the pressure applied to the tissue (e.g., between about 3 kg/cm2 to about 16 kg/cm2); and 2) the gap distance between the electrodes (e.g., between about 0.001 inches to about 0.008 inches). More particularly, accurate application of pressure is important to oppose the walls of the vessel; to reduce the tissue impedance to a low enough value that allows enough electrosurgical energy through the tissue; to overcome the forces of expansion during tissue heating; and to contribute to the end tissue thickness which is an indication of an effective seal.
As an alternative to open electrosurgical forceps for use with open surgical procedures, many modern surgeons use endoscopes and endoscopic electrosurgical apparatus (e.g., endoscopic forceps) or laparoscopic forceps for remotely accessing organs through smaller, puncture-like incisions. As a direct result thereof, patients tend to benefit from less scarring, fewer infections, shorter hospital stays, less pain, less restriction of activity, and reduced healing time. Typically, the forceps are inserted into the patient through one or more various types of cannulas or access ports (typically having an opening that ranges from about five millimeters to about twelve millimeters) that has been made with a trocar. As such, smaller cannulas are typically more desirable relative to larger cannulas. Forceps that are configured for use with small cannulas (e.g., cannulas less than five millimeters) may present design challenges for a manufacturer of electrosurgical instruments.